Pressure bearing lubricating oil



Patented Mar. 1, 1938 PRESSURE BEARING LUBBICATING OIL Arnold J. Morway, New York, N. Y., assignor to Standard Oil Development Company, a corporation of Delaware No Drawing. Application June 19, 1934,

. Serial No. 731,268

10 Claims.

The present invention relates to an improved lubricating composition especially for lubrication under highpressure which is encountered in automobile transmissions or other similar mech- 5 anisms. The invention will be fully understood from the following description.

In recent years more attention has been continually paid to lubrication 'of gears, transmission and other mechanisms operating under 1 heavy loads. The use of hypoid gears has increased the need for compounds carrying. increased loads at higher-speeds. The ordinary compounds used for such service are the socalled leaded" oils which contain lead oleate.

15 The present invention deals with a new composition ior the same general type of service. The composition comprises an oil-soluble zinc salt or soap used in connection with a material rich in sulphur, both of these ingredients being 20 incorporated in a high grade hydrocarbon lubricating oil. As a particularly desirable modiilcation of the broader idea is contemplated a mixture of both lead and zinc soaps'along with the sulphur compound which is much superior 25 to other compounds with respect to the load bearing capacity at high speeds, and particularly with regard to the appearance and condition of the gear teeth and other metal parts.

The zinc salts which are used in the present 30 composition comprise the usual soaps or salts of the high molecular weight organic acids such as oleic, stearic, and mixtures 01' the same such as may be obtained from-tallow and other natural fats. In addition to these commercial fatty 35 acids may be mentioned certain organic acids which are particularly interesting to the petroleum refiners in that they are directly obtainable from petroleum. Among these are included the oil soluble sulphonic acids, those obtained by 40 treating lubricating pils, cracked wax, or other such material with sulphuric acid, especially with concentrated or fuming acid, as in the manufacture of petroleum white oils. Certain alkyl sulphuric acids may also be used, particularly those 45 in which the alkyl group contains at least 10 carbon atoms, and may be obtained by the sulphation of cracked or unsaturated paraflln wax. It is to be understood that these alkyl sulphuric acids are mono-alkyl products of which the 50 alkyl group may be either primary, secondary or tertiary. The other hydrogen atom of the acid.

is to be combined with the zinc salt in the usual manner. Napthenic acids are also contemplated such as are obtained from Roumanian, Russian 55 and certain domestic crude oils either in the (Cl. 8'I-9) natural or cracked condition. Furthermore, certain synthetic acids are also contemplated such as are obtained by the oxidation of paraiiln wax at relatively lowtemperatures with air or other oxidizing agents.

The soaps may be made in any desirable manner, for example, by adding metallic oxide directly to the fatty or other soap acid, and raising the temperature to bring about reaction, or

in an alternative manner by adding inorganic l0 salts of the particular metals, for example, zinc chloride to soda soaps so asto form the heavy metal soap by double decomposition. The soaps are added in the present compositions to the extent of 10 or 20% so as to furnish from 2 to 5% of the metal in final composition. If lead soaps are to be used in combination with the zinc soaps as preferred then they may be used in equimolar'proportions, or more or less of either the one or the other may be used, for example, 3 mols of lead to 1 mol. of zinc or vice versa. The mixture of the'two metals ordinarily gives much, better results than r alone.

The sulphur com ds that are used in the present compositions are of a type ofoil-soluble organic sulphur compounds, and may be obtained from certain sulphur rich crudes especially found in East Texas fields. Corrosive sulphuris preferred to the non-corrosive types and the word corrosiveis used in a special sense to describe that type of compound, including free sulphur, which is capable of discoloring a bright copper strip when applied according to the method ordinarily used for testing gasoline and described by the American Society for Testing Materials.

The corrosive compounds should be suiiiciently high boiling so as not to be lost by evaporation,

and pure compounds may be used instead of the naturally occurring sulphur which was referred 40 to above, for example, high molecular weight mercaptans, polysulphides, preferably trisulphide' or higher, as well as free sulphur itself, which may be added in small amounts. Oleflnes, for example, obtained from cracked wax, or vegetable, mineral and marine ofls may also be sulphurized by cooking with free sulphur or sulphur chloride and sulphurized terpenes, such as sulphurized pine oil may also be employed. The

amount of the corrosive sulphur in the final composition is preferably from'about .3 to about 1%, and the best results are obtained by having this amount of truly corrosive sulphur in addition to any amount of non-corrosive sulphur which i might be present. The amount of truly corrosive u sulphur can be determined as the difference between total sulphur determinations before and after heating with a finely divided metal such as copper.

The oils to which the heavy metal soaps are added should be well refined minerallubricating oils either heavy distillates or residuals, cylinder stocks and the like. They may be obtained from various crudes refined by acid and clay in the usual manner or by solvent extraction, hydrogenation, destructive hydrogenation and similar processes. It has been found that all of the metallic soaps are not readily soluble in all types of mineral oils, especially in the high quality base oils, that is to say, those which have viscosity indices of '70 or and above. In the low quality oils having a viscosity index below about 50 any of the various soaps may be used without difllculty. In the higher quality oils, however, special treatment may sometimes be necessary. For example, the oil may be given a light oxidation treatment with air which for unknown reasons renders it capable of dissolving the various soaps. Onthe other hand, special soluble soaps can be used and among these the lead and zinc naphthenates and sulphonates are probably the most desirable.

In describing these metallic compounds it has been indicated that lead and zinc soaps may be added to the composition. These soaps may be pre-formed in each case and separately added or a mixed soap may be prepared which may be either a mixture of the two soaps or may be a double soap in which the lead and zinc materials are both present in chemical combination. Other addition agents may be present without detriment, for example thickening agents, oxidation and pour point inhibitors, dyes for color or cast, chlorine compounds, esters, alcohol and the like for increased oiliness.

Example I In the following tests the same base oil is used and the'tests were all conducted in the same manner on the Almen machine. This machine and test method have been described in Nat. Pet. News of Nov. 11, 1932. The data is as follows:

and the pin was scored. Nevertheless it was markedly superior to the prior samples. Samples 5 and 6 showed a still greater improvement. These compositions may have been able to carry even greater loads but 15,000 was the limit of the test. Friction was much lower, the curve was smooth and without any sudden rises and the .pin condition was excellently burnished in each case with metallic zinc deposited on the rubbing surfaces of pin and bushing.. The heat development wasnot excessive in either case.

Example I! To a well refined lubricating oil was added 10% of a sulphurized pine oil and 5% each of lead and zinc vnaphthenates. The final composition showed the following analysis and specification:

Viscosity 100 F 1215 Sec. Saybolt Viscosity 210 F 95 Sec. Saybolt Viscosity index Zinc .5%

Lead 1.5%

Total sulphur .8%

Corrosive sulphur .3%

In the Almen test this compound carried the full 15,000 #/sq. in. The frictional curve with load was smooth throughout with a final frictional value of 3.6 inch pounds. The bearing after test was in excellent condition without any indication of scoring or excessive wear and it had a bright zinc coating.

The present invention is not to be limited by any theory of the mechanism by which the soaps afiect the load bearing capacity of the oil nor .to

It is clear from the table that Samples 1, 2 and 3 failed badly and apparently did not increase the load carrying capacity of the oil at all. The final friction was very high, so high in fact as to shear the pin. The fourth sample was much better; it carried the entire test load but the friction curve was not smooth and suddenly mounted at a load of 5000 #/sq. in. The final friction was high, much heat was developed 2. An improved lubricating oil comprising a viscous petroleum hydrocarbon, zinc soap soluble therein, and a corrosive sulphur compound dissolved iri said oil.

3. An improved lubricating oil comprising a viscous petroleum fraction and zinc soap soluble therein, and prepared from an acid containing more than 10 carbon atoms selected from the group of fatty acids, unsaturated acids and organic acids derived from petroleum, and acorrosive compound of sulphur dissolved in said oil.

4. Composition according to claim 3 in which the zinc soap is derived from an acid obtained from petroleum and selected from the class consisting of naphthenic acids, sulphonic acids, alkyl sulphuric acids and acids derived from the oxidation of paraflin wax.

5. Composition according to claim 3 in which a soluble lead soap is present in addition to the zinc soap.

6. Composition of matter according to claim 3 in which the sulphur is present as a compound selected from the group consisting of high boiling mercaptans, p lysulphides and oleflnes, vegetable, animal and marine oils which have been sulphurized.

7. An improved lubricating composition comprising a'viscous petroleum lubricating oil having a viscosity index above 70, zinc naphthenate dissolved therein, and a corrosive sulphur compound dissolved in said oil.

8. Composition according to claim 7 in which lead naphthenate is present in addition to the zinc naphthenate.

9. An improved lubricant comprisinga viscous petroleum oil containing soluble zinc soap of an acid selected from the class consisting of haphthenic and sulphonic acids in proportion to give from about 2 to 5% of zinc in the finished lubri v 

